Rh(III)-Catalyzed Domino [4 + 2] Annulation/Aza-Michael Addition of -(Pivaloyloxy)benzamides with 1,5-Enynes via C-H Activation: Synthesis of Functionalized Aromathecins.

Reported herein are the Rh(III)-catalyzed cascade annulation reactions of -(pivaloyloxy)benzamides with 1,5-enynes to access diversely substituted aromathecin derivatives involving C-H activation. The developed procedure offers an efficient synthetic tool for the assembly of a wide range of -(pivaloyloxy)benzamides and 1,5-enynes with good atom economy and functional group tolerance. The key reactions involved in this annulation are alkyne insertion and aza-Michael addition under oxidant-free mild reaction conditions.

Rh(III)-Catalyzed Cascade Annulations To Access Isoindolo[2,1-b]isoquinolin-5(7H)-ones via C-H Activation: Synthesis of Rosettacin.

An efficient protocol for the synthesis of diversely substituted 7-hydroxyisoindolo[2,1-b]isoquinolin-5(7H)-ones from the reaction of N-(pivaloyloxy)benzamides with 2-alkynyl aldehydes has been developed, which proceeds through sequential alkyne insertion followed by addition of the amide nitrogen on to the aldehyde. This method provided the products with aminal functionality as a handle for further diversification. The synthetic utility of this strategy was successfully illustrated by the concise, two-step synthesis of an alkaloid, rosettacin, and a topoisomerase I inhibitor.